Field of the Invention
The invention lies in the automotive arts. Specifically, the invention relates to a method for the closed-loop control of the boost pressure of an internal combustion engine with a turbocharger. In particular, the method is used for transient variation of the desired boost pressure value for internal combustion engines.
In internal combustion engines, especially diesel engines, that are equipped with a turbocharger, it is necessary for combustion-technical reasons to make defined boost pressures for the filling of the combustion chambers available over the entire operating range. The boost pressure generated by the turbocharger is dependent on the operating point of the engine. In a prior art regulating unit that regulates the boost pressure, the desired boost pressure is taken from an rpm and load-dependent performance graph. The desired values stored in the performance graph are ascertained beforehand with the aid of static test bench experimentation. At low engine speeds (rpm) or low loads, low desired boost pressures are stored in memory.
Motor vehicle operation predominantly takes place in dynamic fashion, however, that is, with frequently changing engine speeds and thus different boost pressures. Specifying desired boost pressures from a performance graph, therefore, is not always satisfactory. Under rapid load changes, for instance during shifting, the speed and load briefly drop sharply, and as a result, the desired boost pressure is reduced in the shifting times in accordance with the performance graph specification as well. The drop in the desired value specification in brief load changes, however, leads to major pollutant emissions and is therefore undesired.
One such system for the closed-loop control of the turbocharging of an internal combustion engine is described in U.S. Pat. No. 5,551,235 to Entenmann et al. (German Patent Disclosure DE 43 44 960).